1. Field of the Invention
The present invention relates to an ultrasonic probe having a plurality of modules, and an ultrasonic diagnostic apparatus.
2. Description of the Related Art
There is an ultrasonic probe which has a plurality of piezoelectric transducers. As applied examples of this ultrasonic probe, there is an ultrasonic probe with two or more modules connected in at least one direction (see, for example, Jpn. Pat. Appln. KOKAI Publication No. 2004-41730).
FIG. 8 shows a transverse cross sectional view of an ultrasonic probe 100 including a plurality of modules 90. The ultrasonic probe 100 has two modules 90. The module 90 has a backing material 91. To the upper of the backing material 91, a plurality of piezoelectric transducers 95 are disposed via a flexible PC board (FPC) 93 having a thickness of W90 (typically 50 μm). The module 90 has 12 piezoelectric transducers 95 along a first direction. Typically, the width W91 along the first direction of the piezoelectric transducer 95 is 250 μm. In addition, the width W93 of a groove between the piezoelectric transducers 95 by dicing is typically 50 μm. Consequently, the center-to-center distance p90 of two adjacent piezoelectric transducers 95b inside the module 90 is 300 μm.
The modules 90 are connected in the first direction by silicone adhesives, etc. and the thickness W96 of an adhesive layer 96 is typically 50 μm. In order to connect the modules 90, or in order to allow the FPC 93 to pass through between surfaces to be connected, the center-to-center distance p91 of two piezoelectric transducers 95a to be connected becomes 400 μm. That is, the distance p91 is wider than the distance p90. As a result, side lobes rise.
In a module of this kind of configuration, sub-dicing is sometimes performed for piezoelectric transducers in order to suppress unrequired vibrations. In this event, assume that part of the piezoelectric transducer 95b which is divided by sub-dicing and has the width W97 is called a piezoelectric transducer piece 95c. The width W98 of a groove generated by sub-dicing is typically 50 μm. Consequently, the width W97 of the piezoelectric transducer piece 95c is 100 μm, and therefore, the effective width W99 (W99=2×W97) of the piezoelectric transducer piece 95c inside the module 90 becomes 200 μm.
As shown in FIG. 8, even if sub-dicing is performed on the piezoelectric transducer 95b, only the piezoelectric transducer 95a at an ends of the module 90 is not sub-diced in order to secure mechanical strength. However, in such event, the width W91 of the piezoelectric transducer 95a is 50 μm wider than the effective width W99 of the piezoelectric transducer 95b. Consequently, applying the same drive voltage to the piezoelectric transducer 95a and the piezoelectric transducer 95b increases the intensity of ultrasonic wave generated from the piezoelectric transducer 95a by about 2 dB from the intensity of ultrasonic wave generated from the piezoelectric transducer 95b. This results in inverse-weighting acoustic distribution and increases side lobes further.